the present invention relates generally to the cleaning of filling machines or pumps and more specifically to sterilizing-in-place rolling diaphragm filling units utilized on filling machines.
Filling machines in which one or more containers such as, bottles, ampules, etc. are individually or simultaneously filled by filling units from a respective nozzle to be lowered into the containers, or held above the containers are known in the art, for example, as described in U.S. Pat. No. 4,212,416 to Bennett. The filling units, sometimes referred to as pumps or metering units, have generally included a piston-cylinder arrangement wherein the piston rod is connected to a piston to both push and pull the piston during a reciprocal intake and discharge stroke of the filling unit.
The filling units or pumping units, generally include five major components, mainly a head, a piston, a cylinder, an inlet valve, and an outlet valve. The head has an internal chamber connecting the cylinder and inlet and outlet valves mounted at appropriate ports. Generally the head has been uniquely designed to receive specific pistons and cylinders, inlet valves and outlet valves. A more universal design is disclosed in U.S. Pat. No. 5,154,589 to Ruhl, et al. The inlet and outlet valves are shown as check valves, spool valves, and duck-bill valves. The piston includes a standard pump with a dynamic seal as well as a rolling diaphragm. A further example of a rolling diaphragm pump which allows controlling the amount of material dispensed through the stroke of the diaphragm is shown in U.S. Pat. No. 4,569,378 to Bergandy. All three of the above patents are incorporated herein by reference.
Whereas the Ruhl, et al. U.S. Pat. No. 5,154,589 is designed for ease of assembly, there is still a need to flush the filling unit when changing materials. The early rolling diaphragm pumps of the Bergandy U.S. Pat. No. 4,569,378 have the advantage of no frictional contact parts in the material flow path, minimal particulate generation and a high degree of accuracy. Although it has been designed with reusable parts, some users have cited an excessive number of working parts to assemble or disassemble the pump even for the reusable product contact parts. For the most part, these costs are related to disassembly, sterilization, and reassembly of the pumps at frequent intervals.
The conventional sterilization techniques for rolling diaphragm pumps require that the pump be completely disassembled, and the diaphragm and fluid chamber along with valving components are autoclaved, rendering all surfaces sterile. This is the only effective method to guarantee that the sterile integrity of the pump is not compromised by the flexing of the diaphragm during operation. Although many reciprocating piston pump systems utilizing rolling diaphragms are presented as Steam-In-Place or Sterilize-In-Place systems, it is not possible to create and maintain a sterile condition in these pumps that extends beyond the sterile boundary edge that is established during the sterilization process. Referring to FIG. 1, a lip 14 of a rolling diaphragm 12 is clamped between flanges surfaces 22 and 32 of the pump housing 10 to form a fluid working chamber as illustrated in FIG. 1.
The sterile boundary edge 16 formed on lip 14 from clamping edge 15, when the prior art Steam-In-Place sterilization regimen is utilized as an alternative to autoclaving, is illustrated in FIG. 2. The representation of sterile boundary edge as a definite line is a simplification for descriptive purposes. The actual boundary may appear as a nebulous zone as depicted in FIG. 2.
As the steam fills the chamber and sterilizes the internal surfaces, a sterile boundary edge is formed where the top surface of the diaphragm meets the surface of the flange of the pump housing. The shading represents the unsterilized area of the surface, and the unshaded portion represents the sterilized area. The irregularity of the sterile boundary edge is due to variables such as the surface roughness of the diaphragm, thickness variations in the diaphragm material, the clamping force, and slight dimensional variations in the flange surfaces. Each pump will establish a different sterile boundary edge pattern after sterilization-in-place. Once the extent of the sterile boundary edge has been established during the internal sterilization process, it cannot be extended without re-sterilization. But the encroachment of the non-sterile edge into the sterile area is possible and highly probable, once the pump begins to function.
In operation, the dynamic forces within the pump impact upon the internal surfaces. The intake valve is actuated to the open position as the piston and diaphragm are withdrawn, causing a negative pressure and drawing fluid into the pump. At the end of the intake stroke, the intake valve is closed, the discharge stroke begins, and fluid is forced out of the pump under positive pressure. Concurrently, the diaphragm is alternately convoluted and fully extended during each cycle causing stretching and flexing of the diaphragm material. The pulsating forces acting upon the diaphragm are resisted by the clamping force around its outer rim, causing tension in the diaphragm fiber.
During this cycling, the sterile boundary edge is displaced and the fluid in the pump is exposed to unsterilized surfaces at various locations along the edge. Thus, the sterile integrity of the pump cavity is compromised. It should be noted here that if the pumps were initially disassembled and autoclaved, the surfaces exposed to the fluid due to flexing of the diaphragm in its seat would be sterile surfaces, and sterility would be maintained in the pump cavity. Thus, internal or in-place sterilization, which relies on the establishment and maintenance of a tenuous and transient sterile edge, is not a viable technique.
Although autoclaving is most certainly an effective procedure for establishing sterility, it has several inherent drawbacks which impact negatively on production efficiency. Removal of components from the machine, disassembly to expose critical internal surfaces, autoclaving, sealing of sterile components in protective bags, reassembly of the components, and re-installation onto the machine are all tedious and time-consuming procedures which result in extended production down-time and elevated operating costs.
It should be noted that C.I.P. is known in the industry as clean-in-place and refers to a procedure which requires a circulation of a sanitizing fluid through the system which washes the system and flushes out particles and debris. Sterilization is not necessarily a result of this procedure. Industry defines S.I.P. as sterilizing-in-place and requires a circulation throughout this system of a sterilizing medium, generally in a gaseous or vaporous state and under pressure, which will penetrate the interior of the system and render it sterile. The present invention is directed specifically to a sterilization-in-place system and not a clean-in-place system.
Thus, it is an object of the present invention to provide a rolling diaphragm pump with a minimal number of parts which can be sterilized-in-place without complete disassembly.
Another object of the present invention is to provide a rolling diaphragm filling unit or pump which can be sterilized in-place.
A further object of the present invention is to provide a truly in-place sterilization of a rolling diaphragm pump.
A still further object of the present invention is to reduce the initial cost and ongoing maintenance expense of rolling diaphragm pumps in sterile filling applications as well as others of general purpose fluid metering.
These and other objects are achieved by a pump housing including a base and head mounted to the base in a working position and a sterilize-in-place position. A flexible rolling diaphragm is positioned and clamped by the base and head in the working position to define between the diaphragm and head a working chamber. A retainer is provided for retaining the diaphragm fixed to the babe when the base and head are in their sterilize-in-place position. The housing elements in their working position, exposes a first area of the diaphragm to the working chamber and in the sterilize-in-place position, exposes a second area greater than and including the first area. This provides a larger area of sterilization which would be beyond the clamping area, than that area exposed in the working position of the head and body. The head defines the first working area and the retainer determines the second larger sterilize-in-place area. A seal is provided between the base and head in both the working and sterilize-in-place positions.
The retainer is in a recess of a head facing the base. The retainer is exterior to the working chamber in the working position of the head and base and is partially exposed to the working chamber in the sterilize-in-place position of the head and base. The retainer may include a ring and a spring for biasing the ring towards the base so as to retain the diaphragm on the base when the head and base are in the sterilize-in-place position. Interconnecting elements connect the head and base for defining the working and the sterilize-in-place positions thereof. These interconnecting elements include a peripheral recess in the head and a pin in the base extending into the peripheral recess for defining at least the sterilize-in-place position. These interconnecting elements also include a clamp for clamping the head and base together in and defining the working position. The pin is removable to allow disassembly of the housing elements.
A method for sterilizing-in-place a diaphragm pump includes exposing a sterilizing area of the diaphragm including and greater than a working area of the diaphragm to a working chamber of the pump. Sterilizing medium is introduced into the working chamber and over the sterilizing area of the diaphragm. Once the cleaning is concluded, a portion of the sterilizing area of the diaphragm is covered so as to expose only the working area of the diaphragm to the working chamber after sterilizing. The working area is exposed by displacing the base and head relative to each other in a first direction while maintaining them joined and while maintaining the diaphragm fixed to the base to expose the sterilizing area. A portion of the sterilized area is covered by displacing the base and head relative to each other in a direction opposite the first direction to clamp the diaphragm between the base and head and to cover a portion of the sterilizing area so as to expose only the working area of the diaphragm. Preferably, the sterilizing fluid is steam introduced through the inlet and maintained in the working chamber at a temperature, pressure and duration to obtain sterility of the working chamber and the sterilizing area of the diaphragm.
Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.